Williams was able to get up and run off the field on his own power and returned to the game later in the drive.

Jon Kitna threw a deep ball to Williams, whose back was turned to Collins when the safety came in and made contact with the back of Williams' head with his helmet. Collins was flagged for unnecessary roughness.

Williams crumpled to the ground face first near the Packers' sideline while Aaron Rodgers and other Packers players hurriedly called for the Cowboys trainers.

After Williams' helmet was taken off, he got up and jogged off the field without assistance. The league is closely monitoring helmet-to-helmet hits, saying they can result in suspension.